The typical carpenter's square has been well known for many centuries and is a very necessary and useful tool in most fields of construction. Hardly anyone, whether professional carpenter or craftsman or mere amateur do-it-yourself home builder, has ever done any woodworking without having had to employ a square at one time or another. The square is the only convenient tool for assuring that two pieces of material have been fitted together exactly perpendicularly to each other, or that a single piece of material has adjacent edges which meet at a right angle. As is well known in many forms of professional or home workshop construction, it is most critical that complimentary pieces of material fit together at a 90.degree. angle, or that individual pieces have adjacent edges which meet at a 90.degree. angle, in order for the finished product to be properly constructed in terms of rigidity, strength and aesthetic appearance.
Although the basic configuration of the carpenter's square has remained unchanged since the square was first developed, many improvements have been made which have substantially increased the efficient utilization of the square, as a result of which many different types of squares exist today. For example, the professional carpenter's square is still nothing more than a single piece of metal formed in the shape of an "L", that is, two legs joined to each other at a 90.degree. angle, each leg having markings thereon to indicate increments of linear measurement. Typically, the legs of this type of square are unequal and between 1 and 2 feet long since the square is used where the pieces of material have large dimensions, such as in the construction of a house.
Another common type of square, known as a try square, is typically found in a basement workshop, and has a rectangular steel blade which has markings adjacent opposite longitudinal edges, usually extending about 6 to 12 inches, depending on the size of the square, and having a handle, generally wooden, rigidly connected to one end of the blade, the handle extending about 3 to 5 inches in length at a 90.degree. angle to the longitudinal axis of the blade. Typically a wooden handle has strips of metal attached to the opposite longitudinal edges thereof, and the handle is thicker than the blade so as to extend outwardly from the blade adjacent to both lateral surfaces. By this arrangement, the metal edge of the handle portion can be placed against one edge of a piece of lumber and the blade will extend across the piece of lumber at precisely a 90.degree. angle to the edge against which the handle of the square is resting. This type of square is extremely useful in measuring off lines across lumber at right angles to the longitudinal edges of the lumber for cutting into shorter lengths, and can also be used to assure that the edges are at a 90.degree. angle to the opposite surfaces of the lumber.
Another type of square normally found in the home workshop has a generally triangular shaped handle which is slideably attached to a steel blade portion of the square so that it can be adjustably positioned on the blade portion in order to preset the square for repetitive scribing, and other uses. For example, if it is desired to draw a line along several pieces of lumber at the same distance from a longitudinal edge of each piece, the handle can be positioned along the blade so that a desired dimension will have the same position relative to a longitudinal edge each time the square is placed on a different piece of lumber, which position could even be the end of the blade remote from the handle. While this is a convenient function of such a square, it requires a relatively complex and expensive construction and a manipulation of the square in order to set it to the desired marking. One advantage of this type of square is that the nature of the handle is such that it often can accommodate a bubble level incorporated into the handle, with the result that the square can also be used as a plumb level to determine whether or not the edge of a piece of material is oriented either vertically or horizontally.
One of the major drawbacks of prior art try squares is that they were not designed to be conveniently and rapidly used in connection with the scribing of lines parallel to the longitudinal edge of a length of stock. In addition, in order to obtain the benefit of an adjustable combination square and plumb level, it has been necessary to obtain one of the more expensive and more complex type of square utilizing the adjustable handle described above. Still further, in connection with the above described type of square having a fixed handle, typically the handle is made of expensive well seasoned hard wood which requires accurate working to obtain a perfectly square alignment with the blade, and careful routing is required in order to provide the space for brass inserts which must be flush with the surface of the wood and which, in combination with rivets, serve to secure the handle to the blade portion of the square. Thus, a well constructed square of this type is relatively expensive.